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PMAT x2
Interphase: Duplicated centrisomes- S Phase DNA is copied.
Prophase: Chromatids shorten and thicken Chromosomes undergo synapses - 2 homologous chromosomes come near eachother - each has 2 chromatids so 4 chromatids aligned next to each other Crossing over occurs - segments of DNA from one chromatid swapped with another - result in genetically new chromatid Chromatids are now genetically different from original 4 chromatids.
Metaphase: Chromatids align in middle Centromeres attach to spindle fibres Independent orientation - 2^pairs - 2^23=8,388,608 ----> variation
Anaphase: Homologous pairs get seperated. Homologous chromosome=2 chromatids 23 chromosomes move to each pole reduction-division
Telophase Nucleus reorganize & chromosomes become chromatin Cytokinesis takes place 2 cells - 23 chromosomes
MEIOSIS 2:
PROPHASE II: Chromatin material condenses Chromosomes contain 2 chromatids attached by a centromere 23 chromatid pairs move to equatorial plate
METAPHASE II: 23 chromatid pairs gather to centre of cell before seperation Spindle attaches to centromere
ANAPHASE II: Centromeres divide and 46 chromatids become known as 46 chromosomes Spindle fibres move one chromosome from each pair to opposite poles 23 chromosomes move to each pole
TELOPHASE II: Chromosomes gather at poles and mass of chromatin formed Nuclear envelope develops, nucleoli reppears and cytokinesis takes place Each cell contains a single set of chromosomes 4 cells produced.
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